The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
The present invention relates to distribution systems (such as electrical power distribution systems), more particularly to methods and apparatuses for identifying or isolating faults (such as electrical faults) pertaining to such systems.
Electrical power distribution systems, such as found in the electrical utility industry and aboard U.S. Naval ships, are subject to developing faults (e.g., failures and defects). The isolation and identification of massive electrical faults serves to minimize the adverse consequences thereof, both electrically and environmentally. For instance, electrical faults can result in burning electrical components which tend to release noxious fumes. Also, electrical faults can create large disturbances in generator fuel efficiencies, leading to incomplete combustion and the concomitant release of hydrocarbons and carbon monoxide into the atmosphere; such happenstance would be especially dire in a shipboard or similarly self-contained environment.
In military contexts, it may be desirable to quickly identify and isolate electrical faults due to combat-induced damage, thus allowing for prolonged operation of combat and other critical shipboard electrical systems. Further, the loss of critical electrical systems may translate to a loss of mission capability of a Navy ship; indeed, the cost of mission failure is potentially incalculable. In civilian contexts, it may be desirable to ensure the continuity of power to vital public facilities and interests such as hospitals, police stations and utilities, especially under exigent circumstances such as when an electrical power system is confronted with natural or other disasters.
Notable is the electrical fault protection technology previously implemented aboard U.S. Naval ships. In the past, the U.S. Navy developed an autonomous coordination logic and incorporated this logic in the xe2x80x9cMulti-Function Monitor Ixe2x80x9d (xe2x80x9cMFM Ixe2x80x9d). This coordination logic was necessary to allow selective coordination among the main distribution circuit breakers in the xe2x80x9cAC Zonal Electric Distribution Systemxe2x80x9d (xe2x80x9cAC ZEDSxe2x80x9d), regardless of plant configuration.
The MFM I unit is an autonomous device that imports line-to-line voltages and line currents, calculates fault current levels and directions, and sends a shunt trip signal to an adjacent circuit breaker if overcurrent thresholds are exceeded for a given time delay. Two time delays are incorporated in the MFM I logic, viz., one for reverse over-currents and another for forward over-currents. Since the shunt trip logic of the MFM I is autonomous, the shunt trip time delays are set to allow selective coordination among other distribution circuit breakers such as the 1600-frame AQB-type switchboard circuit breakers. Selective coordination must also be achieved in a variety of plant configurations, including split plant, single ring and double ring configurations. Consequently, the shunt trip time delays are set at 95 ms for reverse over-currents and 400 ms for forward over-currents. Additionally, the ACB-type breakers may take as long as 55 ms to open once shunt tripped, extending total shunt trip times to 150 ms and 455 ms. Several combinations of shunt trips may be necessary for the isolation of a bus-tie fault, and total fault isolation times vary from 175 ms to over 650 ms.
While the MFM I logic provides selective coordination among the AC ZEDS ACB circuit breakers, the fault isolation times required for autonomous selective coordination are too great for certain purposes; in particular, these fault isolation times are not conducive to maintaining critical combat equipment on-line, thereby allowing fight-through during combat casualty situations.
In view of the foregoing, it is an object of the present invention to enable expeditious identification and isolation of electrical failures in electrical power distribution systems.
It is a further object of the present invention to enable same so as to maintain the operational condition of such systems, especially when such systems are essential or critical in nature.
It is another object of the present invention to provide method, apparatus, computer, computer memory and computer program product for effecting the foregoing and other objects of the present invention.
Typical apparatus embodiments of the present invention are intended for use in association with an electrical distribution system having a plurality of circuit breakers. The inventive apparatus comprises a plurality of devices, and further comprises networking means for the devices. Each device includes an electrical sensor and a computer. Each device is paired with a corresponding circuit breaker. Each computer is capable of: (a) receiving sensory information from the corresponding electrical sensor, wherein the sensory information pertains to at least one location proximate the corresponding circuit breaker; (b) processing the corresponding sensory information into processed electrical current direction information; and, (c) receiving the corresponding processed current direction information which is generated by the remaining devices. Usually, the sensory information which is received by a computer from the computer""s corresponding electrical sensor (i.e., from the electrical sensor included in the same device) pertains to at least two locations proximate the device""s corresponding circuit breaker (i.e., proximate the circuit breaker with which the device is paired), wherein at least two such locations are on opposite sides of the corresponding circuit breaker. Frequently according to inventive practice, each device""s computer has a memory and includes an embodiment of the present invention""s software which resides in the memory; usually, each device""s computer is individually equipped with identical or similar inventive software.
According to typical embodiments of this invention, the inventive apparatus is further capable of processing the cumulative processed electrical current direction information (i.e., the sum total of the device""s own processed electrical current direction information together with all of the electrical current direction information respectively processed by the other networked devices) into processed fault identification information. Moreover, according to many inventive apparatus embodiments, the device""s computer is further capable of regulating (controlling) the corresponding circuit breaker, based on the fault identification information. Furthermore, the devices of the inventive apparatus are preferably networked in a xe2x80x9cself-correctivexe2x80x9d fashion. For example, the present invention""s networking means will typically include a plurality of network links, wherein each network link connects two inventive devices. Upon failure of any network link, each computer is capable of circumventing the failure so as to nevertheless effectuate the receiving of the corresponding processed current direction information which is generated by the remaining devices.
Some inventive embodiments provide computer means having a memory and including a computer program product (e.g., computer software) resident in the memory, while other inventive embodiments provide a memory having a computer program product resident therein, while still other inventive embodiments provide a computer program product which is capable of being resident in a memory or a memory of a computer means. According to usual inventive practice, the same or similar computer program product is resident in the memory of each of plural computer means. Generally in inventive practice, the computer program product comprises a computer useable medium having computer program logic recorded thereon for enabling a plurality of computer means to identify and to choose to isolate a state of defectiveness in an electro-mechanical system for transmitting a transmissible medium. The electro-mechanical system has a plurality of transmission cessation means. Each computer means has a transmission cessation means associated therewith. According to many inventive embodiments, the computer program logic comprises: (a) means for enabling each said computer means to process, into local defectiveness information, data relating to the associated transmission cessation means; (b) means for enabling each computer means to ascertain the state of defectiveness, based on the local defectiveness information; (c) means for enabling each computer means to process, into local transmission direction information, data relating to the associated transmission cessation means; (d) means for enabling each computer means to receive remote transmission direction information, wherein the remote transmission direction information includes an aggregation of the associated local transmission direction information respectively processed by every other computer means, and wherein every other computer means processes, into the associated local transmission direction information, data relating to the associated transmission cessation means; (e) means for enabling each computer means to ascertain the location of the state of defectiveness, based at least on the combination of the local transmission direction information and the remote transmission direction information; and, (f) means for enabling each computer means to determine whether the associated transmission cessation means should be activated.
Also according to many embodiments of this invention is a method for identifying and deciding whether to isolate a state of defectiveness in an electro-mechanical system for transmitting a transmissible medium. The electro-mechanical system has a plurality of transmission cessation means. The inventive method comprises: (a) associating a computer means with each transmission cessation means; (b) using each computer means to process, into local defectiveness information, data relating to the transmission cessation means associated therewith; (c) using each computer means to ascertain the state of defectiveness, based on the local defectiveness information; (d) using each computer means to process, into local transmission direction information, data relating to the transmission cessation means associated therewith; (e) using each computer means to receive remote transmission direction information, wherein the remote transmission direction information includes all of the local transmission direction information respectively processed by every other computer means of data relating to the transmission cessation means associated therewith; (f) using each computer means to ascertain the location of the state of defectiveness, based at least on the combination of the local transmission direction information and the remote transmission direction information; and, (g) using each computer means to determine whether the transmission cessation means associated therewith should be activated.
The present invention is applicable to any electro-mechanical distribution system, such as an electrical distribution system or a fluid (either liquid or gas) distribution system. A circuit breaker in an electrical distribution system would be analogous to a valve in a fluid distribution system. An electrical sensor (e.g., electrical current sensor and/or electrical voltage sensor) would usually be implemented in an electrical distribution system, whereas a fluid pressure sensor would usually be similarly implemented in a fluid distribution system. Although the present invention is primarily described herein in relation to electrical distribution systems, the ordinarily skilled artisan who reads this disclosure will understand how the present invention admits of application to a variety of electro-mechanical systems, whether involving electrical transmission or fluid transmission.
The present invention represents a marked improvement over prior methodologies of affording electrical protection for electrical power distribution systems. The methodology according to the present invention is significantly faster than the protective coordination schemes currently used by U.S. Naval ships and the electric utility industry. The present invention""s xe2x80x9cIntegrated Circuit Breaker Protectionxe2x80x9d (xe2x80x9cICBPxe2x80x9d) software determines the location of the electrical fault within an electrical power grid, and communicates this information to sister devices for action. In short, the inventive software enables the rapid and automatic location and isolation of electrical failures, thus keeping vital electrical power systems operational.
The present invention""s Integrated Circuit Breaker Protection (ICBP) software is contemplated for use aboard U.S. Navy ships to expedite shunt trips of AC zonal electric distribution system (AC ZEDS) protective devices in the event of either main bus faults or internal/downstream switchboard faults. The inventive Integrated Circuit Breaker Protection software is currently being installed in Multi-Function Monitor III (MFM III) production units for application on U.S. Navy ships (in particular, the U.S. Navy""s DDG90AF ships). According to the U.S. Navy""s envisioned application, each xe2x80x9cElectric Power Monitoringxe2x80x9d (xe2x80x9cEPMxe2x80x9d) device is referred to as a xe2x80x9cMulti-Function Monitor IIIxe2x80x9d (xe2x80x9cMFM IIIxe2x80x9d). The U.S. Navy contemplates use of the present invention wherein the inventive software is installed in each of a number of EPM devices. At each EPM (MFM III) location, coordinated shunt trip decisions will be made using system-wide information generated by the inventive ICBP software of the same and other EPM (MFM III) devices.
Typical operation of an inventive Integrated Circuit Breaker Protection software system can be better understood by first comparing electrical power systems to fluid systems (liquid or gas) such as liquid water systems. Water systems and electrical systems are analogous in that the following components serve similar functions: (i) water pipes and electrical cables; and, (ii) water valves and circuit breakers. Water pipes each act as a conduit in which water flows, just as cables each provide a conduit in which electrical current flows. Water valves are used to control the flow of water in pipes, whereas circuit breakers are used to control the flow of electrical current in cables. Water valves are opened to allow water to flow, and are closed (shut off) to prevent water from flowing. Circuit breakers are closed to allow electrical current to flow, and are opened to interrupt the electrical circuit, thereby preventing the flow of current. Water flows in a certain direction, depending on the demand for water; similarly, electrical current flows in a certain direction, depending on the demand for power.
Let us imagine that a water pipe has burst and large amounts of water are flowing towards the ensuing hole in the pipe. In order to halt the flow of water, the valve closest to the damaged area of the pipe is closed, preventing any more water from escaping. By closing the valve closest to the damaged area of the pipe, one seeks to keep as many water customers as possible connected to the water main, upstream of the closed valve. For example, it would not be prudent to shut the water off at the main plant for a burst pipe in a remote neighborhood. Instead, it would be prudent to shut the water off as close to the burst pipe as possible, allowing a maximum number of water customers to remain in service.
A hole in a pipe is similar to an electrical fault on a cable. Water will flow towards the hole in the water pipe, just as electrical current will flow towards an electrical fault on a cable. The present invention""s Integrated Circuit Breaker Protection software includes automated logic to open circuit breakers in the event of an electrical fault, thereby preventing the flow of electrical current and maximizing the number of electrical loads still connected in the electric plant.
Conventionallyxe2x80x94that is, in the absence of inventive practicexe2x80x94a location (e.g., station or terminal) in an electric distribution system includes: (i) circuit-breaking means, for xe2x80x9cbreakingxe2x80x9d a circuit (e.g., electrical switch means for breaking an electrical circuit); and (ii) electrical sensing means for determining the respective conditions (e.g., such as would be pertinent to thresholds relating to a fault or defect) existing, in the circuitry, adjacent to the circuit-breaking means on one or (usually) both sides of the circuit-breaking means. For instance, a location in an electric distribution system can include an electrical switch and at least one electrical measuring device (e.g., a voltmeter and/or an ampmeter) on each side of the electrical switch.
More recently, the U.S. Navy has associated with electric distribution systems a kind of digital apparatus, referred to by the U.S. Navy as an electric power monitoring (EPM) device or unit, which performs the electrical sensing means. An EPM unit is essentially a processor/controller which is equipped with a computer chip and computer software, and which acts as an electrical sensor. An EPM unit is capable of sensing an electrical fault condition (e.g., via sensing voltage and/or current) relating to either or (preferably) both sides of the circuit breaker. In accordance with the present invention, an EPM unit is inventively associated with an electrical distribution system so as to be further capable of sending signals providing electrical information (e.g., directional current information) to any or all of the remaining EPM units which are also inventively associated with the electrical distribution system.
According to typical embodiments of the present invention, each location in the electrical distribution system comprises the combination of a circuit breaking device and an inventive EPM device or unit. The EPM unit includes a computer and electrical sensing means (e.g., current sensing means and/or the combination of current sensing means and voltage sensing means). The computer includes a computer chip, a computer memory, computer software resident in the computer memory, an analog-to-digital converter, and controlling means relating to the corresponding circuit breaker. The EPM unit is provided with software in accordance with the present invention. Each EPM unit is associated with a circuit breaking device and effectively represents a kind of control unit. The present invention uniquely feature computer software which effectuates information gathering and processing not only locally (i.e., as to conditions adjacent to the circuit breaker) but also remotely (i.e., as to conditions adjacent to other, typically, all other, circuit breakers). The information is received from remote locations via a computer communications system or network such as Ethernet.
xe2x80x9cEthernetxe2x80x9d is well known in the art, as it represents the most widely used xe2x80x9cLocal Area Networkxe2x80x9d (xe2x80x9cLANxe2x80x9d) technology. The original (and still popular) version of Ethernet supports a data transmission rate of 10 Mb/s. Newer versions of Ethernet, referred to as xe2x80x9cFast Ethernetxe2x80x9d and xe2x80x9cGigabit Ethernet,xe2x80x9d support data transmission rates of 100 Mb/s and 1 Gb/s (1000 Mb/s), respectively. An Ethernet LAN has been variously known to use coaxial cable, special grades of twisted pair wiring, or fiber optic cable. Ethernet can support both xe2x80x9cBusxe2x80x9d and xe2x80x9cStarxe2x80x9d wiring configurations. Typically, Ethernet devices compete for access to the network using an Ethernet protocol such as that which is referred to as xe2x80x9cCarrier Sense Multiple Access with Collision Detection (xe2x80x9cCSMA/CDxe2x80x9d).xe2x80x9d
According to certain inventive applications contemplated by the U.S. Navy, each circuit breaker in the main electric plant has an associated MFM III unit, and each MFM III unit reads local voltages and currents in the electrical system to determine if a fault exists. If a fault is detected, each MFM III unit executes the present invention""s Integrated Circuit Breaker Protection (ICBP) software. The present invention""s Integrated Circuit Breaker Protection software first attempts to determine the direction of local fault current flows. Since it is desirable to maximize the number of electric loads still connected in the electrical system (e.g., maximizing the number of customers connected to a power system after the fault is isolated), the present invention""s Integrated Circuit Breaker Protection software looks at fault current directions calculated and communicated by other MFM III units in the electrical system. System-wide fault event information is stored locally within each MFM III unit. The inventive ICBP software running in every MFM III unit examines what is occurring throughout the electrical system and determines where the fault is located. Once the location of the fault is determined, the inventive ICBP software determines whether its associated circuit breaker should be opened to help isolate the fault. If the circuit breaker is to be opened, the inventive ICBP software generates a shunt trip signal that is delivered by the MFM III unit to the circuit breaker for it to open.
The inventive process pertaining to the prospective inventive practice by the U.S. Navy, such process being fairly representative of typical embodiments of the present invention, essentially includes the following steps: (i) The MFM III unit reads in local voltages and currents; (ii) The MFM III unit analyzes these voltages and currents to see if a fault is detected in the electrical system; (iii) If a fault is detected, the inventive ICBP software is executed in the MFM III unit to determine the direction of electrical current flow; (iv) The inventive ICBP software organizes data related to electrical fault currents to allow the MFM III unit to pass this data to other MFM III units via Ethernet connections; (v) The MFM III receives data from other MFM III units in the electric plant and passes this data to the inventive ICBP software; (vi) Using data from other MFM III units as well as data generated locally within its own MFM III unit, the inventive ICBP software determines where the fault is located in the electrical system; (vii) The inventive ICBP software determines if it should generate a shunt trip signal to trip the local circuit breaker based on the fault location; (viii) If a shunt trip signal is generated by the ICBP software, the MFM III unit then sends this signal to the local circuit breaker so that it opens to isolate the electrical fault.
The utilization of the present invention""s Integrated Circuit Breaker Protection (ICBP) software aboard U.S. Navy ships will expedite shunt trips of AC zonal electric distribution system (AC ZEDS) protective devices in the event of either main bus faults or internal/downstream switchboard faults. In accordance with such implementation of the present invention, the inventive ICBP software is installed in the aforementioned electric power monitoring (EPM) device, called the Multi-Function Monitor III (MFM III), where coordinated shunt trip decisions are made using system-wide information generated by the inventive ICBP software of the same and other EPM devices.
The U.S. Navy contemplates practicing the present invention using the MFM III unit hardware, which is the U.S. Navy""s next-generation multi-function monitor. In accordance with the present invention, the MFM unit will be capable not only of importing local voltages and currents, but also of collecting system-wide information through communications with other MFM III units. The MFM III will then make a coordinated response to rapidly isolate a main bus fault in an effort to provide fight-through capabilities in a combat damage scenario.
In order to produce a coordinated response, the High Speed Relay (HSR) algorithm, developed by Barrons Associates Inc. (BAI), was originally utilized in the MFM III. Originally designed for radial distribution systems, the HSR algorithm is used only to provide fault detection status and calculate power levels used in other MFM III algorithms. The present inventor, a U.S. Navy employee, was tasked by the U.S. Navy to develop the additional MFM III logic algorithms necessary to take the HSR""s raw power levels and fault detection statuses, and to generate system information necessary to initiate a coordinated shunt trip response among all MFM III units. The shunt trip actions allowed by the MFM III units during a fault event were dictated by Bath Iron Work""s (BIW) xe2x80x9cIntegrated Protective Coordination Systemxe2x80x9d (xe2x80x9cIPCSxe2x80x9d) concepts, written by Mike Sieleman. This IPCS logic was transformed into the Integrated Circuit Breaker Protection (ICBP) software by the present inventor for use in the MFM III units. The inventive ICBP software, designed by the present inventor to inventively implement and improve upon the original IPCS concepts, includes the means to generate the system data used to make the shunt trip decisions in the MFM III.
The present invention""s Integrated Circuit Breaker Protection software, when inventively implemented in the MFM III, allows coordinated shunt trip response among the AC ZEDS main bus-tie circuit breakers, during a casualty event on the main distribution system. A coordinated shunt trip response provides more rapid isolation times (under 100 ms), and the area of isolation is smaller than that achieved using autonomous logic of the MFM I. Smaller areas of isolation allow more load centers to remain connected to the main distribution system after isolation, reducing the need for bus transfers. By isolating the fault event more quickly, the ability of critical combat loads to ride-through a fault event increases, thus potentially improving overall mission capabilities during combat scenarios. Also, faster fault isolation will lessen the effects of electrical fires that may be initiated by fragments impacting energized cables. Finally, smaller areas of electrical isolation will provide a quicker assessment of actual fault location, allowing the ship""s crew to take necessary actions for damage control and electrical plant reconfiguration, if necessary.
The present invention""s Integrated Circuit Breaker Protection software is currently being experimentally utilized in the MFM III prototypes and will eventually be installed in production units for applications on DDG91 Class U.S. Navy ships. Nevertheless, in the light of this disclosure, how the present invention may be practiced in a variety of other applications will be readily apparent to the ordinarily skilled artisan. The inventive software disclosed herein is applicable to any AC ZEDS distribution system, with minor modifications, and can be implemented within or incorporated into future EPM-type devices where voltage and current monitoring is available.
Other objects, advantages and features of this invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings and appendices.
The following appendices, 56 pages total, together represent an embodiment of the Integrated Circuit Breaker Protection software (source code) in accordance with the present invention, and are hereby made a part of this disclosure:
Attached hereto marked APPENDIX A (29 pages) and incorporated herein by reference is that portion of the inventive ICBP software embodiment which represents the Fault Isolation Algorithms, including the Fault Direction algorithm, the Local Buffer Algorithm, the Topology algorithm, the Switchboard Fault Detection algorithm, the Bus Tie Fault Detection algorithm and the Shunt Trip algorithm.
Attached hereto marked APPENDIX B (5 pages) and incorporated herein by reference is that portion of the inventive ICBP software embodiment which represents the Data Update (DU) algorithm.
Attached hereto marked APPENDIX C (9 pages) and incorporated herein by reference is that portion of the inventive ICBP software embodiment which represents the Data Matching (DM) algorithm.
Attached hereto marked APPENDIX D (5 pages) and incorporated herein by reference is that portion of the inventive ICBP software embodiment which represents the Include Files (IF).
Attached hereto marked APPENDIX E (2 pages) and incorporated herein by reference is that portion of the inventive ICBP software embodiment which represents the Remote System Information Handling Routines (RSIHR).
Attached hereto marked APPENDIX F (6 pages) and incorporated herein by reference is that portion of the inventive ICBP software embodiment which represents the Initialization Routines (IR).